Tv vertical deflection circuit



June 5, 1956 B. v. voNDERscHMlTT 2,749,475

TV VERTICAL DEF'LECTION CIRCUIT 2 Sheets-Sheet l Filed. Nov. 2, 1953@femm TTORNI-I Y June 5, 1956 B. v. voNDERscHMlTT 2,749,475

TV VERTICAL' DEFLECTION CIRCUIT Filed NOV. 2, 1955 2 Sheets-Sheet 2 70FIF/f77 552/5551 47 rm 2i INI/ENTOR.

J MMM ATTORNEY United States Patent This invention relates. inpgeneralto. dellection circuits Yfor cathoide ray: tubes and more especially toVapparatus for improving the el'lciencyf diiec'tioncircuitsgdffdisplaytubes in'color television receivers.

t InY conventional monochrome televisionv receivers,y,electromagnetictdeection' for the kinescope' is often employed.

A VVdeflection .yoke which includes vertical. and' horizontalvldeliec'tion coils is' used to supply"'the'necessary 'de'ection fieldsto 'the cathode ray tube or' kinescope. The coils for tliehorizontaland'ver'tical deflection aremountedfphyisi- .cally close nto oneanotherin the 'dellec'tion yke so.that.

a certain 'amount vof .capacity is. .present between the two .sets ofwindings. In ordinary monochrometelevision U1eceivers,flossesdue to'thiscapac'ity are not serious.

"With some "modern colorizt'elevision"'kinescopes, such as the Three GunShadowtMask type which'hasibeen -3.0

well vdescribedian'cl explained in""Part"II;f itheR'CA Review*for'September 1951 atnpage 4'66, et. seq., ajd'iiec'tionyke isiuse'dlwhich is largerthan 'monochrome yokes. "Itl is so 'constructed' thatwhenthe neck of the tricolor kinescope is inserted-through it there ismoreclearance'betweenthe l 'neck'andlhelinterior surface ,oftheyoke `atallpoints thanfexistsin 'monochromeyokes 'This design permits greaterlatitude of adjustment, but since Atheactils are *further "from they'cathodeJay inthe tube, morewpower 'is requiredto createastronger'ield. As a result the 'effectivearea between windingsisincreased and thus the `capacitance'existing between the'horizontalzan'd vertical 'sections `ofthe yoke becomes l4-,orf5,timesugreaterfthan `'that ofr monochromeyokes.

IfA 'the'fvertical winding is returned; through the vertical centeringlpotentiometer to AAC.` ground, this A.ad'clitional vcapacity results"in-excessive increasei'inlfthe retrace ',time of thethorizontaldeection'circuit, loss of. high voltage and' excessive 'ringingresulting in'excessive'vertical 'dis- -placement'which. may 'cause aso-:called"rainbow eiect Ato be explained later. l

AccordingA to rone form lof this" invention, in'ductances are placed'intermediate *the t vertical "ideection windings andyftheivertical'centering potentiometer. Inoue =form ofthe-invention,"the inductancesma-y take the form of .a low capacitybilar transformer. With respect to A.-C. 'theiinductancesl isolate thevertical winding vfrom ground. The-vertical winding thus becomes "aVhigh impedance so V"farfasfthe'v horizontal 'frequencies' are concernedAt' the 4sameA 'timefa` means islprovide'd for supplying vertical cen-#tering'current to the vertical windings. In'another form, @induct-aneesmayl be placed inseries vwith the horizontal .windings-'permitting DSC.tobe'applied to thehorzontal nwinirlings.

x-'Ar principal: object of fthe 'invention is to prevent* interfsactionbetween the# currents in windings of ldeilectonf circuitstforelectromagnetically-'deected cathoderay tubes.

Itzis also z-anrobject fT the @presenti-invention' to improvetherperformance 'of the horizontal idee'ction circuit fby preeniin'gf:excessive retrace l'time ofsthe horizontal sawntooy 2,749,475EY'Patented June 5,', 1956 fice 2 iStill another ,objectof the.inventionv is .the-prevention of undue" loss of anode-voltagederived.fromthe..l1ori .zontal deectionircuit in color. televisionreceivers.

' hand edge of` the. raster.

'.Still ,anothenobject is to` provide amethodof supplying centeringcurrent. to lthevertical Windingsof-,a colon-kinescope yokewithout.,interactiomfrom, .or with,..vthe horizontal deflectionwindings.

Another purposev of. vthe invention. isto` providefamethed ofsupplyingcentering current to the :horizontal deflection windings of acolor-,kinescope Other `objects .of the invention .will .become@apparent from a reading `of the, following specicationftogetherwith'the Vdrawings in which:

lfigure l is a-block diagramof atypical .color tele- VlSlOl'l ICCCIVCI;

.FigureZ depicts schematicallyone'form of the,.inv.en tion as used in'the circuit of the vertical deectionawindings; and

'Figure'f3 Adepicts schematically another vform of rheinvention as usedin the VcircuiLf.thehorizontal.deflection windings.

tions of the `receiver respectively. "The dilerence;.fre

quency for the audio section. of the receiver istfedefrom the'R. F.section 2 to the sound I.F.-section3.where itis amplified. Theamplified, sound-modulated IF. carrieris then -applied to .FM Aaudio,detector 4 which iectively removes the .audioinformationf fromthecarrierandapplies itto audio .amplierLS which drivestheoutputstagewhich maybe a loudspeaker, for example.

The video modulated intermediate'frequency` produced in R. F. section 2`is applied to video l. F.` section where it is amplified. The outputofsectiont is appliedtoan AM video detector 7 where the pictureinformationis extracted. VThe picture informationtisthen ,applied .=tovideo amplifier 8 which may consist of one or more stages ofamplication.

Assuming that .the video signals originallyswereproduced to conform.with .specifications adopted bythe NTSC (National Television VSystemCommittee) ,which from the composite videoY signal appearing in'the'output of ampliiieriS. Inthe Vchrominance'channe1'210`the'liltered,limited bandis detected by means vof So-Called V"synchronousdemodulators. 'The latterxconsist of. means for homodyning the filteredband with .two v'dilerent phases Yof alocally generated set ofoscillationslhaving the same frequencyas a subcarrier onwhichgthe'chromiknance information was originally impressed. As airesult`rof the homodyning action, socalled xfcolor.'diiierence signalsforthegreen, Lredand bluecornpo'nents o'f'the ftelevised objectare'obtained. ThecOIorfdiEerence sig- Anals are filteredinchannelm and'then each is appliedito 4adders 11, 12 and 13. The luminance signal fromchannel 9 is also applied to each of these adders. As a result of theelectrical addition performed by each of the adders 11, 12 and 13, colorsignals for red, blue and green are produced by them respectively. andapplied to the input of a display means such as a three gun shadow mask"color kinescope 14 referred to above.

To deflect properly the three electron beams generated bythe three guns15, 16 and 17 of kinescope 14, the synchronizing and blankinginformation contained in the luminance channel must be utilized. A syncseparator 18 is adapted to receive another portion of the output ofchannel 9. The sync signals for horizontal and vertical deflection arethen employed to actuate horizontal deflection generator 19 and verticaldeflection generator 20'. The latter supply the necessary waves to drivethe horizontal windings 21 and 22 and the vertical windings 23 and 24respectively. Horizontal centering c0ntrol25 is coupled to the windings21 and 22 for providing D. C. for centering purposes. Its exactplacement in certain types of deflection systems is indicated in greaterdetail in Figure 3. It may include circuitry containing a potentiometerfor supplying the D. C. A vertical centering control 26 is coupled tovertical windings 23 and 24 for a similar purpose and its relation tothe kinescope deflection circuit is indicated more particularly inFigure 2.

v The other parts of the kinescope 14 are not shown inasmuch as they arenot pertinent to this invention. Figure 1 shows one type of colortelevision receiver, but it is to be understood that many variations arepossible without departing from the essential spirit of the invention.For example, the sections up to the luminance channel may be of theso-called intercarrier type which is more fully explained in Elements ofTelevision Systems (Prentice-Hall) by G. E. Anner beginning at page 604.

Figure 2 shows in more detail the inter-relation of some of thecircuitry of horizontal and vertical deflection geng erators 19 and 20,horizontal and vertical centering controls and 26, and windings 21, 22,23 and 24. A horizontal oscillator is coupled to the input of tube 27which is the horizontal output driver. The plate of tube 27 is coupledto high voltage transformer 28. A high voltage rectifier stage 29 isalso coupled to one end of transformer 28. The cathode of a damper tube30 is connected to a tap in the transformer 28 and the plate isconnected for A. C. through capacitors 31 and 32 to `the other end oftransformer 28 and to ground. For D. C.

the plate of tube 3) is connected through a coil to B+. From taps atother points of transformer 28, energy is applied through condensers 33and 34 to the windings 21 and 22V which are the horizontal windings ofthe deflection yoke. Horizontal centering control circuit 25 supplies avariable amount of D. C. through windings 21 and 22 for centeringpurposes. In one form the horizontal centering control circuit 25 may becoupled to the circuit as shown and explained in connection with Figure2.

A vertical oscillator (not shown) is coupled to the input electrode of avertical output tube 35 whose plate is coupled to the primary ofvertical output transformer 36. The secondary of transformer 36 iscoupled to the vertical windings 23`and 24. Heretofore it has beencustomary to connect the windings 23 and 24 through non-reactive meansor directly to the moveable arm 39 -and 22, a certain amount of straycapacity exists and is represented by the dashed line condensers labeledCs. In Figure 2 the effect of the stray capacity Cs existing Ibetweenthe horizontal and vertical windings is to couple A. C. energy from thehorizontal windings 21 and 22 to the vertical windings 23 and 24. In thecustomary circuit the A.C. in windings 21 and 22 sees little impedanceto A.C. ground since energy capacitively coupled to windings 23 and 24has a relatively unimpeded path via connections 37 and 38 through theresistance of centering potentiometer 41 and through capacitor 42 toground.

In this form of the invention, instead of returning the verticalwindings 23 and 24 to the vertical centering potentiometer 41 in thevertical centering control 26 directly through connections 37 and 38,they are instead coupled through inductances such as inductances 43 and44 which may be the windings of a bifilar transformer 45, for example.

Since the effect of the stray capacity Cs is to increase the effectivecapacity in the horizontal windings, which may be represented by anequivalent parallel resonant circuit, the frequency of the horizontalsawtooth decreases so that the return or retrace time of the sawtooth isincreased and less second anode voltage is generated. By placing theadditional inductance in the vertical windings, the stray capacity nolonger provides a direct path through the vertical windings to centeringpotentiometer 41 and to A. C. ground for the frequencies from thehorizontal dellection circuit. Effectively the stray capacitance and theinserted inductances, such as inductor 45 are in series and thehorizontal A. C. now sees a high impedance to ground. This reduces theeffective capacity of the deecting yoke resulting in shorter return timeand increased anode power output.

A low voltage power supply 46 is coupled to one end of potentiometer 41.The box 26 is intended to show some of the circuitry that may be used toprovide vertical centering control, although it is to be understood thatmany variations are possible.

Since different impedance levels exist between the vertical windings andthe horizontal windings due to the stray capacity Cs, the amounts ofcurrents transferred from the horizontal to the vertical will differ atdifferent points in the vertical windings. This causes ringing in thevertical deflection sawtooth and consequent displacement of thehorizontal scanning line on the left side of the raster. In the threegun color kinescope 14, each beam is displaced differently in thevertical direction. Consequently the position of the scanning beam foreach color at the beginning of each line of the raster is diverted fromits normal position. A rainbow elfect may be visible at the left handside of the raster for a lateral distance of about one inch. The amountwill vary substantially with the deflection system used. This reducesthe usable area of the color kinescope and the added inductances 43 and44 tend to prevent this phenomenon.

While a bililar inductance such as inductance .l5 possesses relativelylow capacity and performs very efciently, the present invention is notlimited to use of such an inductance. Two ordinary inductances could beused instead but greater inductance values for each of them wouldprobably be required. In addition, the inductances theoretically shouldbe matched very closely which would entail greater expense than bilarwound types.

Figure 3 illustrates the use of inductances placed intermediate thehorizontal windings and the horizontal centering control. A horizontaldriver tube 27 actuated by pulses from a horizontal oscillator (notshown) is coupled to transformer 28 as in Figure 2. The plate of dampingtube 30 is connected to the transformer 28 as in Figure 2 throughcondensers 31 and 32 and to one end of potentiometer 51. The verticalwindings 23 and 24 are coupled to the vertical centering control 26 asshown in Figure 2. A variable width control coil 47 is effectively inparallel with horizontal windings 21 and 22. The latter windings areenergized through condensers 33 and 34 as shown previously in Figure 2.lBetween the horizontal windings 21 and 22 and the horizontal centeringco'utrol shown by box 25 two inductances 48 and 49 which may be thewindings of a bilar wound transformer 50, for example, are interposed.The centering control Z may include a horizontal centering potentiometer51 having a moveable arm 52 and a fixed tap S3 to which inductances 48and 49 are connected. As stated above, the windings 48 and 49 may beindividual inductances which are preferably matched very closely. Thisarrangement permits D.C. to be applied to the horizontal windings andhas the added advantage of providing an impedance to prevent shortingout the section 55 of the transformer 2% insofar as A.C. is concerned.

The invention claimed is:

l. A cathode ray deflection system comprising in combination, firstmeans for deffecting said cathode ray electromagnetically in a firstdirection, second means for deflecting said cathode rayelectromagnetically in second direction, said first and second detiectngmeans being adapted to be energized by currents having an A.C.component, each of said currents having frequencies considerablydifferent from one another, a source of D.C., and at least one inductivemeans coupled to said source for applying said D.C. to at least one ofsaid deflecting means, said inductive means being adapted to preventinteraction of the currents in said first and second deflecting means.

2. A cathode ray deflection system comprising a first inductive meansfor deliecting said ray in a first direction, a second inductive meansfor delecting said ray in a second direction, a source of directcurrent, and third inductive means coupled to said source for applyingsaid D.C. to one of said deecting means, said third inductive meansbeing adapted to present a high A.C. impedance to currents in the otherof said inductive deflecting means to which it is not coupled.

3. A cathode ray deflection system including a first electromagneticdeflection means for defiecting said ray horizontally, a secondelectromagnetic defiecting means for deflecting said ray vertically, asource of D.C., and means for applying said D.C. to said verticaldefiecting means, said applying means including an inductance, saidinductance being adapted to present a high impedance to currents in saidhorizontal deecting means.

4. A cathoderay tube deecting system comprising a horizontal deflectioninductance, a vertical deflection inductance, said inductances being inproximity to one another, a source of D.C. current, said sourceincluding a potentiometer having one terminal substantially at A.C.ground potential, and means coupled to said potentiometer and to saidvertical deflection inductance for applying said D.C. to said verticaldeiiection inductance for centering purposes, said applying meansincluding a high impedance to currents in said horizontal defiectioninductance, said applying means thereby isolating said verticaldeflection inductance from the A.C. ground potential terminal of saidpotentiometer for suppressing A.C. current flow from said horizontaldeflection inductance through said vertical deflection inductance tosaid A.C. ground potential.

5. The invention as described in claim 4 wherein said applying meansincludes a bifilar wound inductance.

6. A cathode ray deflecting system comprising, a hori- 60 zontaldeflection inductance containing a plurality of CII windings in series,a vertical deflection inductance containing a plurality of windings inseries, said horizontal and vertical inductances being in proximity toone another, said horizontal inductance being energized by currentshaving frequencies much higher than the frequencies of currents whichenergize said vertical inductance, a source of D.C. current, said sourceincluding a potentiometer one of whose terminals is effectively at A.C.ground with respect to the currents in said horizontal inductance, afirst inductance coupled to one end of said plurality of verticalwindings and to a point on said potentiometer, and a second inductancecoupled to the other end of said plurality of vertical windings and toanother point on said potentiometer, said first and second inductancesadapted to apply said D.C. to said vertical defiection inductance forcentering purposes, said first and second inductances having essentiallyidentical electrical characteristics, said rst and second inductancesoperating to present a high impedance to currents in said horizontalinductance so as to minimize the flow of currents having frequencies ofthe same order as those in said horizontal windings through saidvertical windings t0 said effective A.C. ground.

7. The invention as described in claim 6 wherein said first and secondinductances are the two windings of a bilar Wound inductance.

8. A cathode ray tube deflecting system comprising, a horizontaldeliection inductance containing a plurality of windings in series, aVertical deflection inductance containing a plurality of windings inseries, said horizontal and vertical inductances being in proximity toone another, a source of D.C., said source including a potentiometer, afirst inductance coupled to one end of said plurality of serieshorizontal windings and to a point on said potentiometer, and a secondinductance coupled to the other end of said plurality of horizontalseries windings and to another point on said potentiometer, said firstand second inductances being adapted to apply said D.C. to saidhorizontal inductance, said first and second inductances havingessentially identical electrical characteristics.

9. A cathode ray tube deflection system comprising in combination ahorizontal deiiection inductance, said horizontal inductance adapted tobe energized by relatively high frequency currents, a vertical deectioninductance placed in proximity to said horizontal inductance, saidvertical inductance adapted to be energized by relatively low frequencycurrents, a resistance element, one terminal of said resistance elementbeing coupled to an effective A.C. ground potential, a first inductancecoupled to one end of said horizontal inductance and to a point on saidresistance element, and a second inductance coupled to the other end ofsaid horizontal inductance and to a different point on said resistanceelement, said first and second inductances having essentially identicalelectrical characteristics and being adapted to apply D.C. from saidresistance element to said horizontal winding.

References Cited in the file of this patent UNITED STATES PATENTS

